1. Field of the Invention
The present invention relates to an electronic mail system which delivers various types of electronic mail information, such as facsimiles, voices, text, etc., transmitted over a communication network to their respective destination terminals.
2. Description of the Related Art
With the recent spread of information communication service, the demand for a system for automatic delivery of various types of information, such as images, voices, text (characters), etc., to remote locations is increasing. To meet the demand, an electronic mail system has come into use which permits free transmission and reception of such information among various types of terminals, such as facsimile equipment, personal computers or telephone sets, over a communication network such as a public communication network.
The electronic mail system has a facility for storing mail information sent from a terminal temporarily in a mail center and delivering the stored mail information to a destination terminal or terminals at time and in a way (for example, one-to-one individual communication, one-to-N broadcast communication) which are specified by a user.
FIG. 1 illustrates the system configuration of a prior electronic mail system.
A number of terminals 1a, 1b, . . . , such as telephone sets, facsimile equipment, etc., are connected to an electronic mail processing apparatus (hereinafter referred to as a mail apparatus) 3 installed in the mail center via a public telephone network or a private telephone network 2.
In general, the electronic mail system provides electronic mail service to subscribers which are assigned their respective identification numbers (subscriber's numbers, ID).
To send mail information to the mail apparatus 3, a user operates push buttons of a telephone in accordance with the following procedure:
(1) The user dials the telephone number of the mail center.
(2) The mail center prompts the user through voice guidance to enter his or her identification number.
(3) The user operates push buttons to enter his or her identification number.
(4) The mail center prompts the user through voice guidance to specify a mail service (individual communication, broadcast communication, etc.) that he or she requests.
(5) The user operates push buttons to specify his or her mail service.
(6) The mail center prompts the user through voice guidance to enter the destination of the mail information.
(7) The user operates buttons to enter the destination (in the case of broadcast communication all the destinations are entered).
(8) The mail center prompts the user to send a message.
(9) The user transmits the message through telephone or facsimile.
In order to send mail information using a mail system it is required, as described above, that user operates buttons on a telephone to enter his or her subscriber's identification number, the type of a mail service that he or she requests, the destination number and so on. These input operations are troublesome and time-consuming. In the case of the one-to-N broadcast communication in particular, the user has to enter destination numbers in succession. Thus, problems arise in that the operations are troublesome and time-consuming and the possibility of operational errors increases.
If a destination number is entered in error, the mail apparatus 3 will send received mail information to the wrong destination. Thus, problems will arise in that others may be troubled by misdelivery of mail information and the leakage of confidential information may be caused.
The following measures have been taken to prevent misdelivery of mail information caused by misentry of destination numbers. That is, subscribers (terminals) of destination are classified into groups (grouping of destinations) and destination information (telephone numbers and facsimile equipment numbers) of subscribers is entered for each of groups, thereby restricting delivery of mail information to subscribers which are not entered (subscribers entered in other groups).
However, the destination grouping method requires that all the destinations should be entered beforehand, which is time-consuming. In the case of broadcast delivery to subscribers in a combination different from that of destinations entered in a group, the destinations of the subscribers have to be entered into the mail apparatus again. Thus, the destination grouping method is not easy to use.